The subject invention is directed to the art of load lifting devices and, more particularly, to a load lifting system adapted for slidable mounting to the bed of a standard pickup truck vehicle for retraction of the entire system into the truck bed. Although the present invention will be described with particular reference to pickup truck and van vehicles, it is to be appreciated that the subject invention has other uses and is equally adapted for use with any vehicle having a flatbed or in other non-vehicle related applications such as, for example, loading docks, fixed support platforms, or the like.
Presently, there are many load lifting devices available on the market that are adapted for mounting to the rear of large delivery trucks, pickup trucks, or other vehicles of the type having a rear cargo deck portion provided for carrying various types of loads. One such system is shown in FIG. 1 whereat a lift gate assembly 10 is illustrated having a generally U-shaped base member 12 connected to a planar lift gate 14 by means of a pair of spaced apart, parallelogram linkages 16, 18. One or more prime movers such as electric motors or hydraulic cylinders 20, 22 as shown, are pivotally connected between the parallelogram linkages 16, 18 at selected fixed mounting locations on the U-shaped base member 12. As the hydraulic cylinders linearly extend when they are actuated, the parallelogram linkages 16, 18 provide for relative vertical movement between the lift gate 14 and the U-shaped base member 12 while simultaneously maintaining the lift gate 14 in a horizontal orientation substantially as shown. In that way, the lift gate 14 is movable between a range of vertical load and unload positions relative to the U-shaped base member 12. The parallelogram linkage mechanism is well known in the art.
Although lift gate devices such as the example illustrated in FIG. 1 have met with some success, one major drawback associated with apparatus of that type configuration is the manner in which they are attached to the rear of target vehicle. More particularly, prior art lift gate assemblies are attached directly to the frame of the target vehicle such as, for example, by bolting or welding the assembly to structural frame members. This being the case, the lift gate assemblies of the prior art remain fixed to the outside of the vehicle during use and, therefore, are exposed to the elements such as snow, rain, dirt, and the like.
Another disadvantage of the prior art lift gate assemblies mounted outside of the vehicle body is that once mounted to the target vehicle frame, they interfere with the use of hitches, winches, step bumpers, or other items normally associated and useful on the rear of truck-type vehicles.
In addition to the above, typical prior lift gate assemblies require modification to the target vehicle such as, for example, the removal of the rear bumper and tailgate in pickup trucks. Since the tailgate provides some security to the contents contained within the pickup truck bed, the removal of same could cause serious security issues with respect to loads that are likely to be stolen from the pickup truck bed.
Further with regard to the required modification to the target vehicle, typical prior art lift gate assemblies include a platform portion that is normally folded up into a vertical orientation when the lift device is not in use or while the vehicle is in motion. In addition to the negative aesthetic aspects of the pickup truck looking unlike a regular vehicle on the road, the position of the lift gate, together with the location of the U-shaped base member, causes interference with the use of truck caps or other pickup bed protective devices including soft protective covers and rigid bed lid devices or the like.
The inability to use a truck cap coupled with the requirement of tailgate removal poses a potentially serious security risk to the cargo loaded in the pickup truck bed. There is little that can be done to protect against theft of the cargo when the vehicle is left unattended.
Lastly, prior art lift gate assemblies such as the example illustrated in FIG. 1 require secondary handling of the load between a position on the lift gate 14 and the storage and transport location within the pickup truck bed. In that regard, the cargo must be pushed, skidded, or dragged into the vehicle from the lift gate prior to folding the lift gate into its locked, vertical orientation for transport of the cargo in the pickup truck bed.
It would be desirable to provide a load lifting system that is adapted to be selectively totally self-contained within the bed of a typical pickup truck so that tailgates and caps could be used. Further, it would be desirable that the load lifting system be slidable on a frame member for horizontal translatory motion relative to the plane defined by the pickup truck bed.
It would further be desirable to provide a load lifting system that is not only slidable so as to be self-contained within the pickup truck bed, but also to provide a load lifting system that enables the use of pickup truck caps, tailgates, and bumpers, hitches, and the like in order that the cargo may be protected against theft and against potentially harmful environmental conditions and, further, to give the vehicle a "regular" outward appearance.